Liquid crystal display device with a counter voltage line intersecting the drain lines

ABSTRACT

An interconnecting structure and a pixel structure suited to large-sized screens are formed. A counter line/electrode is formed on a TFT substrate, and the counter line/electrode is made of a stacked structure film in which a layer made of aluminum or an alloy essentially containing aluminum is covered with a high-melting point metal film, and a transparent conductive film which covers the stacked structure film.

CROSS-REFERENCES TO RELATED APPLICATIONS

The present application is a Continuation Application of U.S.application Ser. No. 09/754,232, filed Jan. 3, 2001, which is related toand claims priority from Japanese Patent Application No. 2000-5856,filed on Jan. 7, 2000.

BACKGROUND OF THE INVENTION

The present invention relates to a liquid crystal display device and,more particularly, to a liquid crystal display device which is calledIn-Plane Switching mode.

Liquid crystal display devices are widely used in various kinds ofelectronic equipment such as display devices such as display monitorsfor personal computers and television receivers. Various types of liquidcrystal display devices are known. A liquid crystal display device ofthe type which is called In-Plane Switching (IPS) mode has a liquidcrystal panel generally made of two substrates disposed in opposition toeach other with a liquid crystal interposed therebetween. In each pixelarea on the surface of either one of the substrates that is in contactwith the liquid crystal, a pixel electrode is formed and, in addition, acounter electrode is formed at a location close to the pixel electrode.This type of liquid crystal display device generates an electric field(lateral electric field) parallel to the surface of the substratebetween the pixel electrode and the counter electrode, therebycontrolling the alignment direction of the liquid crystal in the planebetween the surfaces of the substrates.

In other words, the In-Plane Switching mode of liquid crystal displaydevice is constructed to control the amount of transmission of lightthrough the area between the pixel electrode and the counter electrodeby means of the alignment direction of the liquid crystal to which theelectric field is applied. Although a module which includes a liquidcrystal panel as well as constituent elements such as a driver circuitand an illuminating light source is generally called a liquid crystaldisplay device, the term “liquid crystal display device” to be usedherein collectively indicates both a liquid crystal panel and a liquidcrystal display device.

It is known that such a liquid crystal display device is superior in aso-called wide viewing angle characteristic in that the state of itsdisplay does not vary even if its display screen is observed in obliquedirections.

Each of the pixel electrode and the counter electrode has so far beenformed of a conductive layer which does not allow light to betransmitted therethrough.

It has recently been known, however, that one electrode made of atransparent electrode material is formed over the entire area except theperiphery of a pixel area, while the other electrode made of astripe-shaped or rectangular transparent electrode is formed over theone electrode with an insulating film interposed therebetween. Since thetransparent electrodes are used for the pixel-driving electrodes, aso-called aperture ratio is greatly increased.

The above-described type of art is disclosed, for example, in SID(Society for Information Display) 99 DIGEST: PP. 202-205 and JapanesePatent Laid-Open No. 202356/1989.

In a so-called large-sized liquid crystal display device having anorthogonal length greater than or equal to 46 cm (nominal 18 inches) or51 cm (nominal 20 inches), it has been required to lower the resistanceof counter lines or voltage application lines (gate lines and drainlines) for switching elements such as thin film transistors TFT.

To meet the demand for lower resistances, aluminum or an alloy whichessentially contains aluminum (hereinafter referred to simply asaluminum) is suitably used as the material of such interconnectionlines.

In addition, to improve the luminance of the screen of the liquidcrystal display device, it is desirable that pixel electrodes andcounter electrodes be made of a transparent conductive film (hereinafterreferred to as ITO film or the like) such as ITO (Indium Tin Oxide), IZO(Indium Zinc Oxide) or IGO (Indium Germanium Oxide).

In the case where aluminum is used for gate lines, drain lines orcounter lines, while ITO or the like is used for pixel electrodes orcounter electrodes, it is necessary that ITO or the like whichconstitutes the pixel electrodes and the counter electrodes be stackedon an aluminum film which constitutes such lines, because ofconstructional necessity in the formation of electrical connections anda pixel pattern.

However, since aluminum and ITO or the like greatly differ in corrosionpotential, there are some cases where during the wet etching ofindividual patterns for interconnection lines, pixel electrodes orcounter electrodes, aluminum is dissolved in a developing solution andITO or the like is reduced, and transparency is degraded and thetransmissivity of pixels is lowered to a great extent.

In addition, there are some cases where if a pattern of ITO or the likeis formed after the formation of an aluminum pattern (interconnectingpattern), aluminum is corroded during the etching of ITO or the like andan initial function is lost.

In addition, if an interconnection line is formed of aluminum, it isdifficult to electrically connect ITO or the like, which constitutes anoxide transparent conductive layer, with an aluminum film in the stateof being in direct contact with the aluminum film. For this reason, ifaluminum and ITO or the like are to be brought into electrical contactwith each other, a metal film having a small electrical contactresistance with respect to ITO or the like needs to be separatelydeposited and processed on the aluminum film.

SUMMARY OF THE INVENTION

The present invention solves the various problems of the above-describedrelated arts, and provides a liquid crystal display device having aninterconnecting structure and a pixel structure which are suited tolarge-sized screens.

Therefore, according to the present invention, from among the variouskinds of interconnection lines such as gate lines, drain lines andcounter lines that are required to constitute a liquid crystal displaydevice, at least interconnection lines to be disposed as the sane layeras the gate lines are formed of aluminum or a material which essentiallycontains aluminum, and then the counter electrodes and pixel electrodeswhich constitute pixels are formed by using an amorphous transparentconductive film. Representative aspects of the present invention will bedescribed below.

A liquid crystal display device comprising a pair of substrates, aliquid crystal layer interposed between the pair of substrates, a wiringhaving a stacked structure layer formed on one of the pair ofsubstrates, and a transparent conductive film formed over the wiring,wherein the wiring being included an aluminum layer or an alloy layeressentially containing aluminum, and at least one layer from thefollowing group of molybdenum, aluminum, chromium, tungsten, silver, andcopper.

The advantages of the above-described construction of the presentinvention as well as the reasons for such advantages will be describedbelow in detail.

Since the transparent conductive films (ITO or the like) whichconstitute the gate line and the pixel are formed on the same plane ofthe insulative substrate, it is possible to increase the screen size ofa liquid crystal display device having a high aperture ratio and a highviewing angle.

After the formation of an aluminum line, when ITO or the like isdeposited on the aluminum line as the same layer, a conductive film suchas polycrystalline ITO ordinarily causes a strong cell reaction withaluminum in a developing solution during the development of a resistpattern of ITO or the like, and ITO or the like which is an oxide filmis reduced. As the result, ITO or the like is blackened, and indium Inis separated by, for example, the reaction of In₂ O₅+e⁻→2·In+({fraction(5/2)})·O₂(↑) in the case of ITO (In₂ O₅), so that the transmissivity ofthe conductive film is lowered.

In the case of amorphous ITO or the like, since its corrosion potentialis lower than that of polycrystalline ITO or the like, it is possible toreduce the corrosion potential difference between amorphous ITO or thelike and aluminum. Accordingly, even if aluminum and ITO or the like liein the same layer, a cell reaction in a developing solution isrestrained, and a transparent conductive film such as ITO can bedeveloped on aluminum.

In addition, since such an amorphous transparent conductive film can beetched by weak acid, the underlying aluminum is prevented from beingcorroded during the etching of the transparent conductive film.Accordingly, the use of the amorphous transparent conductive filmenables a transparent conductive film such as ITO to be etched onaluminum.

In addition, in the case where an aluminum line is used, it is possibleto prevent a so-called side hillock without the need for anodization bycovering the end surfaces of an exposed aluminum line with ITO or thelike before a CVD process.

Specifically, if a protective film is not formed on the exposed portionof the aluminum line by anodization, when an insulating film isdeposited by CVD on a stacked line in which molybdenum is stacked as itsupper layer, hillocks grow on its end surfaces, so that an interlayershort-circuit occurs with high frequency. To cope with this phenomenon,a comparatively hard film of ITO or the like which covers the endsurfaces of the exposed aluminum film is deposited at a comparativelylow room temperature of about 120° C. As the result, even if the film ofITO or the like is heated at 300° C. during a CVD process, the aluminumsurface covered with the oxide film (ITO or the like) is stable and theoccurrence of hillocks can be completely prevented.

In this manner, by covering the exposed portion of the aluminum linewith the transparent conductive film, it is possible to improve thebreakdown voltage between the gate line and the drain line or betweenthe gate line and the counter line, whereby it is possible to improvethe reliability of the liquid crystal display device.

To bring the transparent conductive film of ITO or the like and thecounter line into contact with each other, aluminum is oxidized to forman alumina film in one pixel except a terminal portion of molybdenum ora molybdenum alloy or a terminal portion of titanium or a titanium alloyas well as a gate terminal portion. Owing to this alumina film, theintersection of the gate line and the drain line and the intersection ofthe gate line and the counter line are all formed as a stacked structurefilm of alumina and an insulating film such as silicon nitride due toplasma treatment, i.e., CVD treatment, and even if the number of suchintersections are increased owing to an increase in the resolution ofthe liquid crystal display device or because of an electrode structurewhich constitutes a pixel, it is possible to decrease the probability ofoccurrence of an interlayer short-circuit to a great extent.

Moreover, if a disconnection is to be restrained in a gate lineclimb-over portion of ITO or the like, ITO or the like is formed as thelowermost layer, and an aluminum line is formed over the layer withmolybdenum, a molybdenum alloy, chromium or a chromium alloy interposedtherebetween.

In the case where polycrystalline ITO or the like is used, thepolycrystalline ITO or the like is formed as a lowermost layer, and amultilayered structure film which contains molybdenum, molybdenumalloy/aluminum/molybdenum or a molybdenum alloy is formed on the layer.During gate-line development treatment, since aluminum does not appearon the surface of the gate line, it is possible to prevent a cellreaction with the underlying ITO or the like.

In the case where the gate line is formed of a stacked structure film ofan alloy of aluminum and neodymium (Al-Nd alloy) or of pure aluminum andtitanium, a conductive film of amorphous ITO or the like is formed as alayer which underlies the stacked structure film. It is said that Alfilm or Ti film can be made free of hillocks because the orientation ofits crystal grains is aligned. In the case where such a hillock-freealuminum line is used, deposition using CVD can be performed with thesurface of the aluminum line exposed. In addition, since amorphous ITOor the like between which and aluminum the corrosion potentialdifference is small (low) is used as the conductive film of ITO or thelike, it is possible to restrain a cell reaction between the aluminumfilm of the gate line and ITO or the like. The amorphous ITO or the likeis crystallized by heat treatment in a later step so that it can begiven etching resistance which enables it to endure the etching ofaluminum and chromium or molybdenum.

On the supposition that polycrystalline ITO or the like is used, thetransparent conductive film of ITO or the like is formed as thelowermost layer. A stacked structure film ofmolybdenum/aluminum/molybdenum is formed on the layer as the counterline. The lower molybdenum film serves to make contact with thetransparent conductive film of ITO or the like which is formed under thelower molybdenum film, and the upper molybdenum film serves as aterminal of a line. In addition, since the aluminum film is covered withmolybdenum, ITO or the like and aluminum are prevented from makingdirect contact with each other in a developing solution. Accordingly, nocell reaction occurs.

Moreover, in the case where the counter electrode is formed in a solidmanner in the pixel area, a capacitance increases which is formed by anoverlap of the counter electrode and a comb-teeth like pixel electrodewhich is formed over the counter electrode, and this increase incapacitance is added to the counter electrode and the time constantthereof increases. However, if the counter line is made of aluminum oran aluminum alloy, the amount of resistance can be decreased and anincrease in the time constant can be restrained.

As is apparent from the above description, in an In-Plane Switching modeof high viewing angle and high transmissivity, particularly in a liquidcrystal display device having a structure in which each pixel electrodeis formed in a solid manner over a pixel area, it is possible torestrain an increase in the time constant of an interconnection line,and it is possible to easily increase the screen size of the liquidcrystal display device.

In addition, since the gate and counter lines are formed of aluminum oran alloy which essentially contains aluminum, their interconnectionresistance can be decreased, and one of electrodes for pixel driving canbe formed in the same layer as the gate line or electrode out of atransparent conductive film of ITO or the like, and a comb-teeth likeelectrode which is the other electrode is formed on a passivation film(insulating film), whereby the capacitance of both electrodes (stackedcapacitance) can be designed to be minimized.

In addition, since an aluminum line is used, the occurrence of hillockscan be reduced by oxidizing the required portion of the aluminum lineand the occurrence of a display defect such as a smear on the screen isprevented, whereby a highly reliable liquid crystal display device canbe obtained.

Incidentally, the present invention is not limited to any of theabove-described constructions nor any of the constructions ofembodiments which will be described below, and it goes without sayingthat various modifications can be made without departing from thetechnical ideas of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the liquid crystal display device according tothe present invention will be described below in detail with referenceto the following drawings, wherein:

FIG. 1 is a diagrammatic cross-sectional view illustrating theconstruction of the essential portion of a first embodiment of theliquid crystal display device according to the present invention;

FIG. 2 is a plan view diagrammatically illustrating the planeconstruction of the one-pixel portion shown in FIG. 1;

FIG. 3 is an explanatory view showing the effect of the amorphousizationof each of transparent conductive films;

FIG. 4 is an explanatory view of the etching rates of aluminum films andtransparent conductive films for an etching solution;

FIG. 5 is a diagrammatic cross-sectional view illustrating theconstruction of the essential portion of a second embodiment of theliquid crystal display device according to the present invention;

FIG. 6 is a plan view diagrammatically illustrating the planeconstruction of the one-pixel portion shown in FIG. 5;

FIG. 7 is a view of the process of fabricating a gate line and a counterline/electrode;

FIG. 8 is a diagrammatic plan view further illustrating the process ofFIG. 7;

FIG. 9 is a diagrammatic plan view following FIG. 8, furtherillustrating the process of FIG. 7;

FIG. 10 is a diagrammatic plan view following FIG. 9, furtherillustrating the process of FIG. 7;

FIG. 11 is a diagrammatic plan view following FIG. 10, furtherillustrating the process of FIG. 7;

FIG. 12 is a diagrammatic plan view following FIG. 11, furtherillustrating the process of FIG. 7;

FIG. 13 is a diagrammatic cross-sectional view illustrating theconstruction of the essential portion of a third embodiment of theliquid crystal display device according to the present invention;

FIG. 14 is a diagrammatic cross-sectional view illustrating theconstruction of the essential portion of a fourth embodiment of theliquid crystal display device according to the present invention;

FIG. 15 is an explanatory view of the equivalent circuit of the liquidcrystal display device according to the present invention;

FIG. 16 is an explanatory view of one example of driving waveforms of aliquid crystal display device to which the present invention is applied;

FIG. 17 is a plan view showing one example of the state in which anexternal circuit is mounted on the liquid crystal panel of a liquidcrystal display device to which the present invention is applied;

FIG. 18 is a front view showing one example of a display monitor towhich the liquid crystal display device according to the presentinvention is applied;

FIG. 19 is a diagrammatic cross-sectional view illustrating theconstruction of the essential portion of a fifth embodiment of theliquid crystal display device according to the present invention;

FIG. 20 is a diagrammatic cross-sectional view illustrating theconstruction of the another example of a fifth embodiment of the liquidcrystal display device according to the present invention; and

FIG. 21 is a diagrammatic cross-sectional view illustrating theconstruction of the essential portion of a sixth embodiment of theliquid crystal display device according to the present invention.

DESCRIPTION OF THE SPECIFIC EMBODIMENTS

Preferred embodiments of the liquid crystal display device according tothe present invention will be described below.

FIG. 1 is a diagrammatic cross-sectional view illustrating theconstruction of the essential portion of a first embodiment of theliquid crystal display device according to the present invention, anddiagrammatically shows a cross section of either one (a lower substrate)of insulative substrates disposed in opposition to each other with aliquid crystal interposed therebetween.

Referring to FIG. 1, a lower substrate SUB is suitably made of a glasssubstrate, and the inside surface of this lower substrate SUB has a gateline/electrode GT (GL) and a counter electrode/line CT (CL). The gateline/electrode GT (GL) is made of a stacked structure film of analuminum alloy g1 and a molybdenum alloy g2, while the counterelectrode/line CT (CL) is made of a stacked structure film whichincludes the aluminum alloy g1 and the molybdenum alloy g2 and iscovered with a transparent conductive film g3 made of ITO. In FIG. 1,there are shown the gate electrode GT which constitutes a thin filmtransistor TFT, and the portion of the counter electrode CT that isconnected to the counter line CL. Moreover this invention allows to usefor g2, at least one layer from the following group of molybdenum,aluminum, chromium, tungsten, silver, and copper formed on said aluminumlayer or said alloy layer essentially containing aluminum.

These gate line/electrode GT (GL) and counter electrode/line CT (CL) arecovered with a gate insulating film GI, and a semiconductor layer, whichis made of a semiconductor film ASI and a semiconductor film N⁺ ASIwhich constitutes a contact layer, is formed over the gate electrode GT.Source/drain electrodes SD1 and SD2 are separately formed over thesemiconductor layer ASI. In FIG. 2, the electrode SD1 is shown as asource electrode, while the electrode SD2 is shown as a drain electrode.

An insulating film PAS is formed to cover the source electrode SD1 andthe drain electrode SD2 as well as the counter electrode/line CT (CL). Apixel electrode PX is deposited above the counter electrode/line CT(CL), and is connected to the source electrode SD1 through a contacthole, i.e., a through-hole TH.

FIG. 2 is a plan view diagrammatically illustrating the planeconstruction of the one-pixel portion shown in FIG. 1. In FIG. 2, symbolDL denotes a drain line, and the portions denoted by the other symbolscorrespond to portions identical to those shown in FIG. 1. In this typeof liquid crystal display device, one pixel is formed in an areasurrounded by two drain lines DL and two gate lines GL (one of which isshown).

The counter line CL is disposed to traverse this one pixel area, and thecounter electrode CT is connected to the counter line CL and is formedapproximately over the entire area of the one pixel. The thin filmtransistor TFT is formed in the intersection of one of the drain linesDL and the gate line GL and the gate line GL serves as the gate line GL,and the drain electrode SD2 extends from the drain line DL, while thesource electrode SD1 is connected to the pixel electrode PX through thethrough-hole TH.

The fabrication of the construction shown in FIGS. 1 and 2 is asfollows. First of all, the aluminum (Al) alloy g1 and the molybdenum(Mo) alloy g2 are deposited in that order to form a stacked structurefilm on the glass substrate SUB. A photoresist is applied to thisstacked structure film, and is dried and patterned. Then, the stackedstructure film is subjected to wet etching using an etching solutionwhich essentially contains phosphorus, thereby forming the gateline/electrode GT (GL) and the counter line CL.

Titanium (Ti) may be substituted for the molybdenum alloy g2. Iftitanium is used, a stacked film of aluminum and titanium is patternedin batch by a dry etching process. The aluminum alloy g1 is suitably analloy such as an aluminum-neodymium alloy (Al—Nd) which is superior inhillock resistance or an aluminum-silicon alloy (Al—Si), or pure Al. Thefirst embodiment uses an aluminum-neodymium alloy (Al—Nd).

In the case where the molybdenum (Mo) alloy g2 is used as a layeroverlying the aluminum alloy g1, a molybdenum-chromium alloy (Mo—Cr) isused which slows down in dry etching rate for a gas which essentiallycontains fluorine.

The etching rates for both films g1 and g2 are individually controlledby adjusting the composition of the materials of the above-describedstacked structure film and the composition of the etching solution,whereby each processed edge has a forward taper as shown in FIG. 1.

Then, the amorphous ITO film g3 is deposited as the counter electrode CTwhich is a transparent electrode. Instead of ITO, IZO (indium zincoxide) or IGO (indium germanium oxide) may be used.

In the case of ITO, when ITO is deposited at room temperature by addingwater during the deposition, the resultant ITO film is amorphousized.However, because of the deposition at room temperature, the ITO film canbe crystallized through heat history in a CVD step. In the case of IZOand IGO, even if IZO or IGO is deposited at a substrate temperature of200° C., the resultant IZO or IGO film becomes amorphous and can,therefore, obtain an amorphous structure with its high substrateadhesion maintained.

FIG. 3 is an explanatory view showing the effect of the amorphousizationof each of such transparent conductive films, and shows the differencesin corrosion potential among crystalline ITO, amorphous ITO, IZO(originally amorphous), molybdenum (Mo) and aluminum (Al) in adeveloping solution (a resist developing solution). Incidentally, thedeveloping solution used when the corrosion potentials were measured wasNMD (a TMAH (tetra-methyl ammonium hydroxide) 2.38% solution).

As shown in FIG. 3, the corrosion potential of aluminum (Al) in thedeveloping solution is the lowest, and the corrosion potentials ofmolybdenum (Mo), IZO, amorphous ITO and crystalline ITO become higher inthat order. If aluminum (Al) and any of the transparent conductive films(IZO, amorphous ITO and crystalline ITO) are immersed in the developingsolution, a cell reaction based on the corrosion potential differencetherebetween occurs, and aluminum (Al) is oxidized and the transparentconductive film is reduced.

In the case of ordinary crystalline ITO (polycrystalline ITO), thecorrosion potential difference between the ordinary crystalline ITO andaluminum is large, so that their reactions vehemently occur and causedamage to themselves, respectively. On the other hand, in the case ofamorphous ITO, the corrosion potential difference between the amorphousITO and aluminum is small compared to the polycrystalline ITO, althoughit depends on the composition of materials to be used for the amorphousITO. Accordingly, the amorphous ITO can restrain damage from beingcaused to each material film during development.

FIG. 4 is an explanatory view of the etching rates of aluminum films andtransparent conductive films for an etching solution. The etching ratesare shown as relative values. The etching solution uses oxalic acid oraqua regia of low hydrochloric acid concentration. In the case of aquaregia of high hydrochloric acid concentration or hydrobromic acid (HBr),since the etching rate of aluminum is high compared to polycrystallineITO, damage occurs in an aluminum film lying immediately below an ITOfilm during the etching of the ITO film. On the other hand, in the caseof oxalic acid or aqua regia of low hydrochloric acid concentration, theetching rate of an amorphous ITO film is higher than that of an aluminumfilm. Accordingly, during the etching of a transparent conductive filmsuch as the amorphous ITO film, damage to the aluminum film directlybelow the amorphous ITO film is not caused.

The counter electrode which is the transparent electrode is in contactwith the counter line via the molybdenum alloy or titanium which is afilm overlying the counter electrode. At the interface between themolybdenum alloy or titanium and ITO which is the counter electrode,since the contact resistance is low, good contact characteristics can beobtained.

In addition, since the aluminum alloy exposed on the side edge surfacesof the counter line is covered with ITO, a hillock does not occur in alater CVD step for formation of the gate insulating film and the like.

After that, the gate insulating film, the semiconductor layer film, andthe semiconductor film for providing contact are respectively formed bycontinuously depositing SiN, an amorphous Si film, an N⁺ amorphous Sifilm by plasma CVD.

Then, the amorphous Si film which forms the semiconductor layer film andthe N⁺ amorphous Si film which forms the semiconductor film forproviding contact are processed by dry etching, thereby preparingisland-shaped semiconductor films to form the source electrode and thedrain electrode. The source electrode and the drain electrode aredeposited by sputtering and patterned by a photolithographic technique,and interconnection lines are processed by wet etching. An alloy whichessentially contains chromium or molybdenum is used as the material ofthe interconnection lines. The alloy which essentially contains chromiumis a stacked material of chromium-molybdenum/chromium (Cr—Mo/Cr). Thealloy which essentially contains molybdenum is a molybdenum-chromiumalloy (Mo—Cr) having high resistance to dry etching.

After the etching of the source electrode and the drain electrode, thecontact layer of a channel portion is removed by dry etching with thesame etching mask, thereby forming a channel.

After that, the passivation layer is deposited by a CVD method. Thecontact hole is formed in a portion of the source electrode by dryetching. In addition to this through-hole, through-holes arerespectively formed in the terminal portions of the gate electrode, thecounter electrode and the source electrodes. To prevent a metal filmitself from being etched by drying etching in the uppermost portion ofany of the gate electrode, the counter electrode and the sourceelectrode, a material whose drying etching selection ratio is 5 or morewith respect to SiN is used.

After that, ITO or the like is again formed as the transparentconductive film which constitutes the pixel electrode. This ITO film isformed in a comb-teeth like shape by a photolithographic technique(refer to the pixel electrode PX shown in FIG. 2). This transparentconductive film may be crystalline or amorphous. If a crystallinetransparent conductive film is to be used, aqua regia of highhydrochloric acid concentration or hydrobromic acid (HBr) is used. If anamorphous transparent conductive film is to be used, oxalic acid or aquaregia of low hydrochloric acid concentration is used.

If a crystalline transparent conductive film is processed withhydrobromic acid (HBr) or an amorphous transparent conductive film isetched with oxalic acid, the amount of side etching can be madeextremely small. Accordingly, this process is suited to the formation ofa fine comb-teeth-like transparent electrode such as that shown in FIG.2 (the pixel electrode PX).

According to the first embodiment, since the thin film transistor TFT,the individual interconnection lines and the individual electrodes areformed over the substrate (TFT substrate) in the above-described manner,it is possible to provide a liquid crystal display device which has thefine transparent comb-teeth like electrode (the pixel electrode PX) andthe plane transparent electrode (the counter electrode CT) and is,therefore, greatly improved in optical transmissivity. In addition,although the capacitance at the intersection of the transparentelectrodes increases, interconnection resistance is decreased and anincrease in time constant can be restrained, because aluminum is usedfor the counter line.

The plane transparent electrode (CT) is formed in a solid shape whichcovers the entire pixel, but even if the plane transparent electrode(CT) is formed in the shape of comb teeth which alternate with the teethportions of the upper comb-teeth like electrode (PX), as in an ordinaryIPS type of liquid crystal display device, the aperture ratio of theliquid crystal display device can similarly be improved.

FIG. 5 is a diagrammatic cross-sectional view illustrating theconstruction of the essential portion of a second embodiment of theliquid crystal display device according to the present invention, anddiagrammatically shows a cross section of either one (a lower substrate)of insulative substrates disposed in opposition to each other with aliquid crystal interposed therebetween. FIG. 6 is a plan viewdiagrammatically illustrating the plane construction of the one-pixelportion shown in FIG. 5. FIGS. 7 to 12 are views illustrating theprocess of fabricating a TFT substrate of the second embodiment.Moreover this invention allows to use for g2, at least one layer fromthe following group of molybdenum, aluminum, chromium, tungsten, silver,and copper formed on said aluminum layer or said alloy layer essentiallycontaining aluminum.

FIG. 7 is a view of the process of fabricating a gate line and a counterline/electrode, and FIGS. 8 to 12 are plan views of the essentialportion of the TFT substrate, further illustrating the process shown inFIG. 7.

In the second embodiment, the inside surface of a lower substrate SUB1has a gate line/electrode GT (GL) and a counter line CL each formed ofan aluminum film g1. The gate line/electrode GT (GL) has an alumina filmg4 which covers the entire surface of the aluminum film g1, and thecounter line CL has the alumina film g4 which similarly covers the uppersurface of the aluminum film g1, and also has a film g2 of molybdenum ortitanium (in the second embodiment, molybdenum) which is formed in aportion of the alumina film g4 in such a manner as to extend from theupper surface of the alumina film g4 to the aluminum film g1.

Incidentally, in terms of an improvement in the quality of oxide film,it is effective to form a coated type of glass film SOG on the glasssubstrate SUB1 in order to promote the oxidation of the surface of theAL film.

A transparent conductive film ITO which constitutes the counterelectrode CT covers the alumina film g4, and is formed approximatelyover the entire area of the pixel area, as shown in FIG. 6, and isformed to make good contact to the aluminum film g1 which constitutesthe counter line CL, via the molybdenum film g2 deposited on a portionof the top of the aluminum film g1. A specific position of themolybdenum film g2 is shown in FIG. 6. Incidentally, the plan shape ofthe molybdenum film g2 is not limited to the rectangular shape shown inFIG. 6, and may be a diamond shape, a circular shape (including anelliptical shape), or a combination of plural appropriate shapes.

The alumina film g3 which covers the aluminum film g1 of the counterline CL does not make good contact to the transparent conductive filmITO which constitutes the counter electrode CT stacked on the aluminafilm g3. Accordingly, the molybdenum film g2 is deposited to extend fromthe upper surface of the alumina film g3 to the underlying aluminum filmg1, thereby improving the contact between the counter line CL and thecounter electrode CT.

Then, as in the first embodiment described above in connection withFIGS. 1 to 4, a gate insulating film GI, a semiconductor film ASI, asemiconductor film N+ASI, a source electrode SD1, a drain electrode SD2,an insulating film PAS, and a pixel electrode PX are formed over thegate line/electrode GL (GT), the counter line CL and the counterelectrode CT.

The process of fabricating the second embodiment will be described belowwith reference to FIGS. 7 to 12. As shown in Step (1) of FIG. 7, astacked structure film of the aluminum alloy (in the second embodiment,an aluminum-neodymium alloy: Al—Nd) film g1 and the molybdenum alloy ortitanium alloy or chromium alloy (in the second embodiment, amolybdenum-chromium alloy: Mo—Cr) film g2 is formed and patterned toform the gate line/electrode GL (GT) and the counter line CL. A planview of this state is diagrammatically shown in FIG. 8.

Then, a photoresist REG is formed on a portion which makes contact tothe transparent conductive film ITO which constitutes the counterelectrode CT to be formed on the Mo—Cr film g2 which is a layer tooverlie the counter line CL (Step (2) of FIG. 7). This photoresist REGis formed into a predetermined pattern through the application of aphotoresist material and exposure and development thereof through amask.

The substrate SUB1 having the photoresist REG formed over the counterline CL is subjected to etching, whereby the Mo—Cr film g2 is removedexcept the portion thereof which underlies the photoresist REG. At thesame time, the Mo—Cr film g2 which overlies the gate line GL is alsoremoved (Step (3) of FIG. 7).

The surface of the Al—Nd film g1 is oxidized with the photoresist REGleft, and the alumina film g4 is formed over the portion of the counterline CL which excludes the remaining Mo—Cr film g2 as well as over thesurface of the gate line GL (Step (4) of FIG. 7). Incidentally, in thissurface oxidation, the thickness of the Al—Nd film g1 exposed on thesurface of the substrate SUB1 is slightly reduced due to the formationof the alumina film g4. A plan view of this state is diagrammaticallyshown in FIG. 9.

After that, the photoresist REG is removed to expose the Mo—Cr film g2(Step (5) of FIG. 7). The exposed Mo—Cr film g2 becomes a contact film.

After the removal of the photoresist REG, the amorphous transparentconductive film g3 is deposited to cover the counter line CL, therebyforming the counter electrode CT (Step (6) of FIG. 7). A plan view ofthis state is diagrammatically shown in FIG. 10.

In the second embodiment, the counter electrode CT has a plane shape,but it may be processed into a comb-teeth like shape in the case ofordinary IPS mode.

The above-described ITO or the like is used as the amorphous transparentconductive film g3. A major part of the aluminum alloy (Al—Nd) film g1which constitutes the gate line GL and the counter line CL is coveredwith the alumina film g4 so that the surface of neither of the aluminumfilm g1 and the counter electrode CT does not directly contact anetching solution. Accordingly, a crystalline transparent conductive filmmay also be used as the transparent conductive film g3.

After the formation of the counter electrode CT, the semiconductor layerASI and the semiconductor layer N⁺ ASI which serves as a contact layer,the source electrode SD1, the drain line DL and the drain electrode SD2are formed as shown in FIG. 11.

Furthermore, after the formation of the insulating film PAS, as shown inFIG. 12, a through-hole TH is formed to extend to the source electrodeSD1 through the insulating film PAS, and a pixel electrode PX made of acomb-shaped transparent conductive film is formed (refer to FIGS. 5 and6).

In the second embodiment, since the gate line/electrode GL (GT) and thecounter line CL both of which use the aluminum alloy are subjected tosurface oxidation treatment, it is possible to prevent a decrease inbreakdown voltage and achieve a great improvement in reliability, ascompared with the case in which interlayer insulation is realized withonly the gate insulating film GI (SiN). In addition, since the contactportion of the counter line CL which is a non-anodized portion has astacked structure of molybdenum which is a high-melting point metal,molybdenum/titanium, molybdenum/chromium or the like, a hillock can becompletely prevented from occurring on the aluminum film.

FIG. 13 is a diagrammatic cross-sectional view illustrating theconstruction of the essential portion of a third embodiment of theliquid crystal display device according to the present invention, anddiagrammatically shows a cross section of either one (a lower substrate)of insulative substrates disposed in opposition to each other with aliquid crystal interposed therebetween.

In the third embodiment, ITO or the like is formed on the inside surfaceof a TFT substrate SUB1 as an amorphous transparent conductive film g3.The counter line CL is made of a stacked structure film which has achromium, molybdenum or titanium film g2 as a base (a lower layer) andan aluminum alloy (such as Al—Nd) film g1 as an upper layer.

Both the chromium, molybdenum or titanium film g2 which is the lowerlayer constituting the counter line CL and the amorphous transparentconductive film g3 which constitutes the counter electrode CT have goodcontact characteristics.

During etching treatment for patterning the stacked structure film ofthe aluminum alloy film g1 and the chromium, molybdenum or titanium filmg2, cell reactions based on the corrosion potential difference betweenthe upper and lower layers in a developing solution occur in both of theupper and lower layers which constitute the stacked structure film. Torestrain the cell reactions, an amorphous transparent conductive filmwhich enables such corrosion potential difference to become small isused. In the third embodiment, a 120 film is used.

Incidentally, a transparent conductive film is not formed between thegate line/electrode GL (GT) and the glass substrate SUB1.

According to the third embodiment, since the transparent conductive filmg3 which constitutes the counter electrode CT is directly formed on theglass substrate (TFT substrate) SUB1, there is not a “pattern climb-overportion” in which a pattern climbs over an interconnection line, andtherefore, a problem such as a disconnection caused by the patternclimb-over portion does not occur. Accordingly, it is possible to obtaina liquid crystal display device having high reliability. Moreover thisinvention allows to use for g2, at least one layer from the followinggroup of molybdenum, aluminum, chromium, tungsten, silver, and copperformed on said aluminum layer or said alloy layer essentially containingaluminum.

FIG. 14 is a diagrammatic cross-sectional view illustrating theconstruction of the essential portion of a fourth embodiment of theliquid crystal display device according to the present invention, anddiagrammatically shows a cross section of either one (a lower substrate)of insulative substrates disposed in opposition to each other with aliquid crystal interposed therebetween.

In the fourth embodiment, a film g3 of amorphous or polycrystalline ITOor the like is formed on the inside surface of a TFT substrate SUB1 as atransparent conductive film which constitutes a counter electrode CT,and a stacked structure film (three-layer structure film) made of amolybdenum or titanium film g2, an aluminum film g1 and a molybdenum ortitanium film g6 is formed on the film g3. Incidentally, the film g3 ofITO or the like is not formed below the gate line/electrode GL (GT).

Since the aluminum film g1 which constitutes the stacked structure filmunderlies the molybdenum or titanium film g6, the surface of thealuminum film is prevented from making direct contact to an etchingsolution during the patterning of the stacked structure film.Accordingly, since the aluminum film and the transparent conductive filmnever coexist in the same etching solution, a cell reaction based on thecorrosion potential difference between both films does not occur.Incidentally, the molybdenum or titanium film g2 which constitutes abase (underlying layer) for the aluminum film g1 of the stackedstructure film improves the adhesion of the aluminum film g1 to thetransparent conductive film g3 which constitutes a base for themolybdenum or titanium film g2 in the case of the counter line CL, aswell as the adhesion of the aluminum film g1 to the glass substrate SUB1in the case of the gate line/electrode GL (GT).

In the fourth embodiment, since each of the counter line CL and the gateline/electrode GL (GT) is the above-described three-layer structurefilm, the transparent conductive film g3 which constitutes the base forthe counter line CL does not need to be amorphous, and may also adoptcrystalline ITO or the like.

According to the fourth embodiment, as in the case of the thirdembodiment, since the transparent conductive film g6 which constitutesthe counter electrode CT is directly formed on the glass substrate (TFTsubstrate) SUB1, there is not a “pattern climb-over portion” in which apattern climbs over an interconnection line, and therefore, a problemsuch as a disconnection caused by the pattern climb-over portion doesnot occur. Accordingly, it is possible to obtain a liquid crystaldisplay device having high reliability.

The driving, structure and application examples of the liquid crystaldisplay device according to the present invention to which any of theabove-described embodiments is applied will be described below.

FIG. 15 is an explanatory view of the equivalent circuit of the liquidcrystal display device according to the present invention. As shown inFIG. 15, a liquid crystal panel which constitutes the liquid crystaldisplay device has a display portion formed by an assembly of pluralpixels arrayed in matrix form, and each of the pixels is constructed tobe able to individually modulate and control transmitted light from aback light arranged at the back of the liquid crystal panel.

Gate lines GL, counter lines CL and drain lines DL are formed over aneffective pixel area AR of an TFT substrate SUB1 which is oneconstituent element of the liquid crystal panel. The gate lines GL andthe counter lines CL are disposed to be extended in the x direction (therow direction) of the effective pixel area AR and to be juxtaposed inthe y direction (the column direction) of the same. The drain lines DLare disposed to be extended in the y direction and to be juxtaposed inthe x direction. Each of the gate lines GL and the counter lines CL hasa construction according to any of the above-described embodiments. Aunit pixel is formed in each of the rectangular areas surrounded by thegate lines GL and the drain lines DL.

The liquid crystal display device is provided with a vertical scanningcircuit V and a video signal driver circuit H as an external circuit ofthe liquid crystal panel. A scanning signal (voltage) is sequentiallysupplied to each of the plural gate lines GL by the vertical scanningcircuit V, and in synchronism with that timing, a video signal (voltage)is supplied to the drain lines DL from the video signal driver circuitH.

Each of the vertical scanning circuit V and the video signal drivingcircuit H is supplied with electric power from a liquid crystal drivingpower source circuit POW, and picture (video) information from a hostCPU such as a personal computer or a television receiver circuit isseparated into display data and a control signal and inputted to thecircuits V and H by a controller CTL.

FIG. 16 is an explanatory view of one example of driving waveforms of aliquid crystal display device to which the present invention is applied.In FIG. 16, a counter voltage to be applied to each counter electrodevia the corresponding counter line is formed as an alternating currentrectangular wave having two values V_(CH) and V_(CL), and thenon-selection voltage of each scanning signal V_(G)(i−1) and V_(G)(i) isvaried between two values V_(CH) and V_(CL) at intervals of one scanningperiod in synchronism with the counter voltage. The amplitude of thecounter voltage and the amplitude of the non-selection voltage is madethe same.

A picture (video) signal voltage is a voltage obtained by subtracting ½of the amplitude of the counter voltage from a voltage to be applied tothe liquid crystal layer.

The counter voltage may also be a direct current voltage, but byalternating the counter voltage, it is possible to decrease the maximumamplitude of the picture (video) signal voltage, whereby it is possibleto use a low-breakdown-voltage type of video signal driver circuit(signal-side driver) H.

FIG. 17 is a plan view showing one example of the state in which theexternal circuit is mounted on the liquid crystal panel of a liquidcrystal display device to which the present invention is applied.Mounted on the peripheral portion of the liquid crystal panel PNL are afirst driver circuit board PCB1 on which a vertical scanning circuit Vis disposed, a second driver circuit board PCB2 on which a video signaldriver circuit H is disposed, and a power supply circuit board PCB3. Thefirst driver circuit board PCB1 and the second driver circuit board PCB2are each made of a so-called flexible printed circuit board FPC.

The vertical scanning circuit V has plural driver IC chips CH11 mountedby a film carrier method (TCP method), and the output bumps of each ofthe driver IC chips CH11 are respectively connected to gate signalterminals GTM of the liquid crystal panel, while the input bumps of thesame are respectively connected to terminals on the first driver circuitboard PCB1.

Similarly, the video signal driving circuit H has plural driver IC chipsCH12 mounted by a film carrier method (TCP method), and the output bumpsof each of the driver IC chips CH12 are respectively connected to gatesignal terminals DTM of the liquid crystal panel, while the input bumpsof the same are respectively connected to terminals on the second drivercircuit board PCB2.

The power supply circuit board PCB3 is connected to the video signaldriver circuit H on the second driver circuit board PCB2 via a flatcable FC, and this video signal driver circuit H is connected to thevertical scanning circuit V on the first driver circuit board PCB1 via aflat cable FC.

Incidentally, the present invention is not limited to this type ofliquid crystal display device, and can, of course, be applied to aso-called COG (Chip On Glass) scheme in which a semiconductor chip whichconstitutes each circuit is directly disposed on a TFT substrate SUB1and the input/output bumps of the semiconductor chip are respectivelyconnected to terminals (or interconnecting layers) formed on the TFTsubstrate SUB1.

FIG. 18 is a front view showing one example of a display monitor towhich The liquid crystal display device according to the presentinvention is applied. This display monitor has a display part in whichthe liquid crystal display device according to any of theabove-described embodiments of the present invention is disposed, anddisplays a picture on its liquid crystal panel PNL. The display part issupported by a stand part. This display monitor is not limited to a typeto be connected to an external signal source which is not shown (apersonal computer or a television receiver circuit), and the externalsignal source may also be built in the stand part or in the peripherythereof.

FIG. 19 is a diagrammatic cross-sectional view illustrating theconstruction of the essential portion of a fifth embodiment of theliquid crystal display device according to the present invention, FIG.19 shows an example that this patent is applied on IPS devices. Thesource comb-teeth like electrodes and the counter comb-teeth likeelectrodes are fabricated with metal. In this case, the amorphoustransparent conductive film is used as lead films, which is notillustrated in FIG. 19. As an another example, the fabrication of sourcecomb-teeth like electrodes with the transparent film makes it possibleto increase transmissivity by decreasing shield area. This example isshown in FIG. 20.

FIG. 21 is a diagrammatic cross-sectional view illustrating theconstruction of the essential portion of a sixth embodiment of theliquid crystal display device according to the present invention, FIG.21 shows an example that the counter comb-teeth like electrodes isfabricated with the amorphous transparent conductive film. The counter(common) electrodes PX are fabricated on the passivation layer made ofacrylic resin OP. The gate electrodes are formed with the layeredstructure which consists of refractory metal and aluminum film. Theamorphous ITO or IZO film are adopted as the counter electrodes so asnot to damage gate aluminum films on development and wet etching processof the transparent films. When a network of the counter electrode arefabricated on both scanning and data bus lines, the aperture ratio canbe improved because of no metal counter electrodes in the pixels. Inthis case, the passivation layer consists of layered CVD deposited SiNfilm and the acrylic resin film in order to decrease inter-wiringcapacitance between the counter electrodes and the gate and drain SD2bus lines.

When the electric resistance of the transparent counter electrodes istoo high, common bus lines running parallel to scanning line arefabricated on the same layer of gate electrodes. In this case, thetransparent counter electrodes is connected to the metal common buslines in each pixel at the through-holes, which is formed simultaneouslyin the layered passivation films.

According to the present invention, it is possible to obtain a highlyreliable and bright picture display. It is characteristic that amorphoustransparent film is etched after Al gate interconnects fabrication. Onthe other hand, the transparent electrodes may be formed on differentlayers from the gate electrodes on the other device structure. Thispatent is effective on the case of the fabrication of transparentelectrodes on Al interconnects. According to the present invention, fromamong the various kinds of interconnection lines such as gate lines,drain lines and counter lines that are required to constitute a liquidcrystal display device, at least interconnection lines to be disposed asthe same layer as the gate lines are formed of aluminum or a materialwhich essentially contains aluminum, and then the counter electrodes andpixel electrodes which constitute pixels are formed by using anamorphous transparent conductive film. Representative aspects of thepresent invention will be described below.

(1) An insulative substrate has an interconnection line which a stackedfilm in which an aluminum layer or an alloy layer which essentiallycontains aluminum is covered with a high-melting point metal layer iscovered with a transparent conductive film.

(2) The insulative substrate has thin film transistors, gatelines/electrodes, drain lines/electrodes, and counter lines/electrodes,and at least one kind of line/electrode selected from among thelines/electrodes is made of a stacked structure film covered with atransparent conductive film, the stacked structure film including analuminum layer or an alloy layer essentially containing aluminum, and ahigh-melting point metal layer which covers the aluminum layer or thealloy layer.

(3) A liquid crystal display device includes:

-   -   a thin film transistor having a gate line/electrode, a drain        line/electrode and a source electrode on either one of a pair of        substrates disposed in opposition to each other with a liquid        crystal interposed therebetween;    -   a counter line arranged in or near a pixel area surrounded by        two gate lines and two drain lines, and a counter electrode        connected to the counter line and formed in a solid manner        approximately over the whole of the pixel area; and    -   a pixel electrode having an approximately comb-like shape        connected to the source electrode and formed over the counter        electrode with an insulation layer interposed therebetween,    -   each of the gate lines/electrodes and/or the drain        lines/electrodes and the counter lines being formed of a stacked        structure film including an aluminum layer or an alloy layer        essentially containing aluminum and a high-melting point metal        layer which covers the aluminum layer or the alloy layer, the        counter electrode being formed as a transparent conductive film        formed in a solid manner approximately over the whole of the        pixel area.

(4) A liquid crystal display device includes:

-   -   a thin film transistor having a gate line/electrode, a drain        line/electrode and a source electrode on either one of a pair of        substrates disposed in opposition to each other with a liquid        crystal interposed therebetween;    -   a counter line arranged in or near a pixel area surrounded by        two gate lines and two drain lines, and a counter electrode        connected to the counter line; and    -   a pixel electrode having an approximately comb-like shape        connected to the source electrode and formed over the counter        electrode with an insulation layer interposed therebetween,    -   each of the gate lines/electrodes and/or the drain        lines/electrodes and the counter lines being formed of a stacked        structure film including an aluminum layer or an alloy layer        essentially containing aluminum and a high-melting point metal        layer which covers the aluminum layer or the alloy layer, the        counter electrode being formed as a transparent conductive film        conductively connected to the high-melting point metal layer.

(5) A liquid crystal display device includes:

-   -   a thin film transistor having a gate line/electrode, a drain        line/electrode and a source electrode on either one of a pair of        substrates disposed in opposition to each other with a liquid        crystal interposed therebetween;    -   a counter line arranged in or near a pixel area surrounded by        two gate lines and two drain lines, and a counter electrode        connected to the counter line;    -   a pixel electrode having an approximately comb-like shape        connected to the source electrode and formed over the counter        electrode with an insulation layer interposed therebetween,    -   each of the gate line/electrode and the drain line/electrode        having an alumina layer over an aluminum layer or an alloy layer        essentially containing aluminum, the counter line having an        alumina layer over an aluminum layer or an alloy layer        essentially containing aluminum and a high-melting point metal        layer formed to extend through the alumina layer from a surface        side of a portion of the alumina layer to the aluminum layer or        an alloy layer essentially containing aluminum, the counter        electrode being formed as a transparent conductive film        conductively connected to the high-melting point metal layer.

(6) The alloy which essentially contains aluminum is an aluminum-rareearth alloy in which an rare earth element is added to aluminum, and anyone or two or more of neodymium Nd, yttrium Y, lanthanum La and samariumSm are used as the rare earth element.

(7) The high-melting point metal is any one or two or more of molybdenumMo, chromium Cr, tungsten W and titanium Ti.

(8) The transparent conductive film is any one of amorphous ITO (IndiumTin Oxide), amorphous IZO (Indium Zinc Oxide) and amorphous IGO (IndiumGermanium Oxide).

(9) Each of the gate line and the counter line uses a stacked film inwhich the upper surface of an aluminum layer is covered with ahigh-melting point metal such as molybdenum Mo or titanium Ti or with analloy of the high-melting point metal, and a plane pixel electrode madeof an amorphous transparent conductive film is formed in the same layeras the gate line and the counter line, and a comb-teeth like electrodemade of an amorphous transparent conductive film is formed as thecounter electrode in the same layer as the source and drain lines orover an insulating film (PAS film).

The film of the high-melting point metal such as molybdenum Mo ortitanium Ti which overlies the portions of the gate line and the counterline that are in contact with the counter electrode made of atransparent electrode and which lies in a portion except gate terminalsand counter terminals is removed by etching, and the resultant exposedaluminum surface is oxidized to form an alumina film.

(10) The gate line is formed of an aluminum/neodymium (Al/Nd) alloywhich overlies a high-melting point metal such as molybdenum Mo, and anamorphous transparent conductive film is formed as a layer whichunderlies the gate line.

(11) On the supposition that polycrystalline ITO is used, thepolycrystalline ITO is formed as the lowermost layer, and molybdenum,aluminum and molybdenum (Mo/Al/Mo) are stacked on the polycrystallineITO as the gate line and the counter line.

As is apparent from the foregoing description, according to the liquidcrystal display device of the present invention, from among the variouskinds of interconnection lines such as gate lines, drain lines andcounter lines that are required to constitute the liquid crystal displaydevice, at least interconnection lines to be disposed as the same layeras the gate lines are formed of aluminum or a material which essentiallycontains aluminum, and then the counter electrodes and pixel electrodeswhich constitute pixels are formed by using an amorphous transparentconductive film. Accordingly, it is possible to provide a liquid crystaldisplay device capable of displaying a highly reliable and brightpicture.

1. A liquid crystal display device comprising: a pair of substrates; aliquid crystal layer interposed between said pair of substrates; drainlines and gate lines formed on one of said pair of substrates andcrossing each other in a matrix form, wherein a region bounded by a pairof said drain lines and a pair of said gate lines defines a pixel; aswitching element associated with and disposed relative to each pixel; asheet-like counter electrode comprising a transparent conductive filmarranged at each pixel; a counter voltage line formed on said counterelectrode, said counter voltage line including a multi-layered structurecomprising a first molybdenum layer, followed by an aluminum layer or analloy layer comprising essentially of aluminum, followed by a secondmolybdenum layer; a first insulating layer formed on said counterelectrode and said counter voltage line; a second insulating layerformed on said first insulating layer; and a pixel electrode comprisinga transparent conductive film that is electrically connected to saidswitching element, wherein said counter voltage line intersects saiddrain lines through said first insulated film, wherein said countervoltage line has a first width where it intersects said drain lines anda second width where it does not intersect said drain lines, said firstwidth being different from said second width.
 2. The liquid crystaldisplay device according to claim 1, wherein said pixel has a widthgreater than said first width.
 3. The liquid crystal display deviceaccording to claim 2, wherein at least one of said first molybdenumlayer and said second molybdenum layer comprises an alloy layercomprising essentially of molybdenum.
 4. The liquid crystal displaydevice according to claim 2, wherein said pixel electrode has anapproximately linear-shaped structure, zigzag-shaped structure, slitshape structure, or comb-shaped structure.
 5. The liquid crystal displaydevice according to claim 4, wherein said pixel electrode extends in thesame direction as said gate lines.
 6. The liquid crystal display deviceaccording to claim 2, wherein said transparent conductive film of saidpixel electrode and of said counter electrode each includes one of ITO,IZO and IGO.
 7. The liquid crystal display device according to claim 6wherein said transparent conductive film is a polycrystalline.
 8. Theliquid crystal display device according to claim 6 wherein saidtransparent conductive film is amorphous.
 9. The liquid crystal displaydevice according to claim 6, wherein said transparent conductive film ofsaid pixel electrode and of said counter electrode are differentmaterials.
 10. The liquid crystal display device according to claim 9,wherein said transparent conductive film is a polycrystalline.
 11. Theliquid crystal display device according to claim 9, wherein saidtransparent conductive film is amorphous.
 12. The liquid crystal displaydevice according to claim 2, wherein said switching element is a thinfilm transistor and said first insulating layer is a gate insulatinglayer of said thin film transistor.
 13. The liquid crystal displaydevice according to claim 1, wherein said counter voltage line extendsin the same direction as said gate lines.